Abstract: The prospects for the facile biosynthesis of drugs coupled with the manipulation of the human microbiome is fraught with therapeutic possibilities. However, the same caveats that exist for the delivery of drugs via ingestion or injection apply to the microbial delivery of drugs. In particular, a therapeutic regime for administration must be established that is efficacious but not harmful. For years, one means of ensuring the longer-term delivery of drugs in specified amounts has been to develop particles, pills, or patches that maintain the controlled or sustained release of drugs into the system. We propose a new paradigm for controlled release, in which controlled release is driven by controlled biosynthesis, which in turn relies on an underlying, modular regulatory mechanism. We establish a separate ?engine? for the expression of therapeutic cargoes, relying on the highly orthogonal T7 RNA polymerase (T7 RNAP), and develop a variety of circuits that lead to regulated gene expression in different patterns of therapeutic relevance, such as homeostatic production of constant concentrations of a drug (Aim 1). We then apply this ?engine? to the production of the amino acid L-DOPA in a known probiotic strain, E. coli Nissle (Aim 2). And then finally the controlled production circuitry in the probiotic species is introduced into mouse models in order to determine how programmed regulatory circuitry can impact the pharmacokinetics and pharmacodynamics of a drug in an organism (Aim 3). The strains are ultimately tested in a chronic progressive degenerative MitoPark mouse model of Parkinson?s disease currently being used in our collaborator?s laboratory at Iowa State University (Aim 3.3).